The present invention relates generally to the field of magnetic data storage and retrieval systems. More particularly, the present invention relates to a magnetic recording head with a writer portion having a rounded top pole.
In an electronic data storage and retrieval system, a transducing head typically includes a writer for storing magnetically-encoded information on a magnetic disc and a reader for retrieving that magnetically-encoded information from the magnetic disc. The reader typically consists of two shields and a magnetoresistive (MR) sensor positioned between the shields. Magnetic flux from the surface of the disc causes rotation of the magnetization vector of a sensing layer of the MR sensor, which in turn causes a change in electrical resistivity of the MR sensor. This change in resistivity of the MR sensor can be detected by passing a current through the MR sensor and measuring a voltage across the MR sensor. External circuitry then converts the voltage information into an appropriate format and manipulates that information as necessary.
The writer portion typically consists of a top and a bottom pole, which are separated from each other at an air bearing surface of the writer by a gap layer, and which are connected to each other at a region distal from the air bearing surface by a back gap closer or back via. Positioned between the top and bottom poles are one or more layers of conductive coils encapsulated by insulating layers. The writer portion and the reader portion are often arranged in a merged configuration in which a shared pole serves as both the top shield in the reader portion and the bottom pole in the writer portion.
To write data to the magnetic media, an electrical current is caused to flow through the conductive coils to thereby induce a magnetic field across the write gap between the top and bottom poles. By reversing the polarity of the current through the coils, the polarity of the data written to the magnetic media is also reversed. Because the top pole is generally the trailing pole of the top and bottom poles, the top pole is used to physically write the data to the magnetic media. Accordingly, it is the top pole that defines the track width of the written data. More specifically, the track width is defined by the width of the top pole near the write gap at the air bearing surface.
In magnetic recording, it is desirable to improve the areal density at which information can be recorded and reliably read. This desire has led to a trend toward shorter bit length along a magnetic recording track and a shrinking track width. Narrow track widths are achieved by use of narrow pole tips at an air bearing surface (ABS) of the head. However, the pole width must be large in the body region of the head where the coil passes between the poles. The larger pole width is necessary to gain adequate magnetic flux through the poles by the coil write current. Hence, it is common to taper the pole from the larger width in the body region to a narrower width in the pole tip region at the ABS.
The top pole in conventional writer designs has a generally triangular shape in the pole tip area. Furthermore, the top pole is typically made of materials that do not have strong intrinsic uniaxial anisotropy. As a result, the shape anisotropy of the top pole is a dominating factor governing domain formation in the top pole. Shape anisotropy of the top pole in the pole tip area results in formation of a domain wall pinned at or near the pole tip. Also, magnetic flux from domains adjacent to the pole tip induces a high remanence in the pole tip. This can result in on-track erasure of data. Plus, magnetization reversal in the pole tip coincides with domain wall motion across the tip. Thus, in conventional top pole designs domain wall motion can be rather slow and irregular and, consequently, magnetization reversal in the pole tip can also be slow.
Therefore, a top pole is needed in which faster magnetization reversal occurs and in which domain walls do not form in the pole tip area.